Environment variables and remote configuration

Environment variables configure a process when it starts. Featurevisor global variables are typed settings that your application evaluates for each context, and they change when it loads a new datafile. This page shows which settings belong where, and how to move one across.

Choose where each setting belongs#

Setting	Typical home
Database credentials or signing keys	Your secret management system
Service address needed before configuration can load	Deployment or process configuration
Support email that varies by country	A Featurevisor global variable
Payment methods selected for a customer context	A Featurevisor global variable
A label that changes with an experiment variation	A variable inside a Featurevisor feature

Anyone can read a datafile sent to a browser or a phone, so keep secrets out of them. A flag does not authorize anything either, so check permissions on your server.

Move one setting at a time#

A process setting might currently look like this in Node.js:

const supportEmail = process.env.SUPPORT_EMAIL || '[email protected]'

Define the configuration value in a Featurevisor project:

variables/supportEmail.yml

description: Support email shown in checkout
type: string
defaultValue: [email protected]

After loading a datafile, evaluate it through an instance named f:

const context = {
  country: 'nl',
}
const supportEmail =
  f.getVariable('supportEmail', context) ??
  process.env.SUPPORT_EMAIL ??
  '[email protected]'

The environment variable stays as a fallback while you move over. Once the value is in Featurevisor, overrides can give different users different addresses, which an environment variable cannot.

supportEmail gives Dutch users support-nl@example.com and everyone else support@example.com.

Moving a setting also changes who can change it. An environment variable usually needs whoever deploys the service and a restart. A global variable changes through a reviewed pull request that anyone on the team can open, and reaches running applications with the next datafile.

Understand when values change#

Changing the definition, publishing the datafile, loading it in the application and evaluating the setting are separate steps. If your application reads a value once at startup, a new datafile does not change the copy it already holds.

Evaluate where the value is needed, or evaluate again on the SDK's datafile_set event. React's hooks do this for you.

Remote configuration, for targeting and tests
Environments and sets, for configuration per environment
Node.js example

Choose where each setting belongs#

Move one setting at a time#

Understand when values change#

Related#